• Journal of Mechanical Science and Technology
• /
• v.18 no.6
• /
• pp.1042-1051
• /
• 2004

The vortex flow characteristics of a sharp-edged delta wing at high angles of attack were studied using a computational technique. Three dimensional, compressible Reynolds-averaged Navier-Stokes equations were solved to understand the effects of the angle of yaw, angle of attack, and free stream velocity on the development and interaction of vortices and the relationship between suction pressure distributions and vortex flow characteristics. The present computations gave qualitatively reasonable predictions of vortical flows over a delta wing, compared with past wind tunnel measurements. With an increase in the angle of yaw, the symmetry of the pair of leading edge vortices was broken and the vortex strength was decreased on both windward and leeward sides. An increase in the free stream velocity resulted in stronger leading edge vortices with an outboard movement.

• Wind and Structures
• /
• v.31 no.3
• /
• pp.229-240
• /
• 2020

In the present work, the main features of primary vortices and the vorticity concentrations downstream of vortex bursting in crossflow plane of a delta wing with a sweep angle of Λ=70° were investigated under the variation of the sideslip angles, β. For the pre-review of flow structures, dye visualization was conducted. In connection with a qualitative observation, a quantitative flow analysis was performed by employing Particle Image Velocimetry (PIV). The sideslip angles, β were varied with four different angles, such as 0°, 4°, 12°, and 20° while angles of attack, α were altered between 25° and 35°. This study mainly focused on the instantaneous flow features sequentially located at different crossflow planes such as x/C=0.6, 0.8 and 1.0. As a summary, time-averaged and instantaneous non-uniformity of turbulent flow structures are altered considerably resulting in non-homogeneous delta wing surface loading as a function of the sideslip angle. The vortex bursting location on the windward side of the delta wing advances towards the leading-edge point of the delta wing. The trajectory of the primary vortex on the leeward side slides towards sideways along the span of the delta wing. Besides, the uniformity of the lift coefficient, C_L over the delta wing plane was severely affected due to unbalanced distribution of buffet loading over the same plane caused by the variation of the sideslip angle, β. Consequently, dissimilarities of the leading-edge vortices result in deterioration of the mean value of the lift coefficient, C_L.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.10
• /
• pp.7-15
• /
• 2006

The effects of strake incidence-angle on the vortex characteristics and the wing-surface pressure distribution for a double-delta wing with strake were investigated experimentally. The strake incidence-angle of negative sign(strake is pitched down from the main-wing upper-surface) increased the suction pressure of the wing-upper surface, which was the same effect of increase of angle of attack. This change of the suction pressure was caused by the closer movement of the vortex cores to the wing upper surface rather than the increase of the vortex strength.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.5 no.2
• /
• pp.83-90
• /
• 2002

An experimental study was conducted to investigate the effects of a leading edge extension(LEX) on the vortex flow field over a delta wing by measuring the total pressure distribution in a subsonic wind tunnel. Freestream velocity was 40m/sec and Reynolds number per meter was $1.76{\times}10^6$. The wing with the LEX experienced a strong interaction between the LEX and wing vortices. As the angle of attack increased, the coupled vortex field of these two vortices maintained its strength and concentricity much better than the vortex field over the wing without the LEX.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.2109-2114
• /
• 2003

The vortex flow characteristics of a yawed LEX-delta wing at a high-angle of attack are studied using a computational analysis. The objective of the present study is to investigate and visualize the effects of the yaw angle, the development and interaction of vortices, the relationship between the suction pressure distributions and the vortex flow characteristics. Computations are applied to the three dimensional, compressible, Navier-Stokes Equations. In computations, the yaw angle is varied between 0 and 20 degree at a high-angle of attack. Computational predictions are compared with the previous experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.8
• /
• pp.16-23
• /
• 2006

The effects of strake planform shapes on the vortex formation, interaction, and breakdown characteristics of double-delta wings were investigated through pressure measurements of upper wing surface and off-surface flow visualization. Three different shapes of strakes were attached to a delta wing respectively to form double-delta wing configurations and tested in a medium-sized subsonic wind tunnel. The results of the pressure measurements indicated that the strake planform having a higher sweep angle generated more concentrated vortex systems at upstream locations, which, however, tended to diffuse and break down much faster at the downstream locations. It was also found from the off-surface visualization results that the cause for the vortex concentration was due to the acceleration of coiling and merging processes between the wing and strake vortices.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.105-108
• /
• 2002

Highly swept leading edge extension(LEX) applied to delta wings has greatly improved the subsonic maneuverability of contemporary fighters. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack$(15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ})$ and six measuring sections$(30\%,\;40\%,\;50\%,\;60\%,\;70\%,\;80\%)$ of chord length. Distributions of time-averaged velocity vectors and vorticities over the delta wing model were compared along the chord length direction. High-speed CCD camera which made it possible to acquire serial images is able to get the detailed information about the flow characteristics occurred on the delta wing. Especially quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarity the significance of the LEX existence.

• 한국가시화정보학회:학술대회논문집
• /
• 2003.11a
• /
• pp.39-42
• /
• 2003

Leading edge extension(LEX) in a highly swept shape applied to a delta wing features the modern air-fighters. The LEX vortices generated upon the upper surface of the wing at high angle of attack enhance the lift force of the delta wing by way of increased negative suction pressure over the surfaces. The present 3-D stereo PIV includes the Identification of 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criterion and so on. A delta wing model with or without LEX was immersed in a circulating water channel. Two high-resolution, high-speed digital cameras$(1280pixel\times1024pixel)$ were used to allow the time-resolved animation work. The present dynamic stereo PIV represents the complicated vortex behavior, especially, in terms of time-dependent characteristics of the vortices at given measuring sections. Quantities such as three velocity vector components, vorticity and other flow information can be easily visualized via the 3D time-resolved post-processing to make the easy understanding of the LEX effect or vortex emerging and collapse which are important phenomena occurring in the field of delta wing aerodynamics.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.771-774
• /
• 2002

Highly sweep leading edge extensions(LEX) applied to delta wings have greatly improved the subsonic maneuverability of contemporary fighters. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack($15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ}$) and six measuring sections of chord length($30{\%},\;40{\%},\;50{\%},\;60{\%},\;70{\%},\;80{\%}$). Sideslip effect in case of the LEX was also studied for two sideslip(yaw) angles($5^{\circ},\;10^{\circ}$) at one angle of attack(20). Distribution of time-averaged velocity vectors and vorticity over the delta wing model were compared along the chord length direction. Quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarify the significance of the LEX existence. Animation presentation in velocity distribution was also implemented to reveal the effect of LEX with wing vortex interaction.

• Journal of Mechanical Science and Technology
• /
• v.18 no.12
• /
• pp.2273-2283
• /
• 2004

The vortical flows over sharp-edged delta wings with and without a leading edge extension have been investigated using a computational method. Three-dimensional compressible Reynolds-averaged Navier-Stokes equations are solved to provide an understanding of the effects of the angle of attack and the angle of yaw on the development and interaction of vortices and the aerodynamic characteristics of the delta wing at a freestream velocity of 20 m/s. The present computations provide qualitatively reasonable predictions of vortical flow characteristics, compared with past wind tunnel measurements. In the presence of a leading edge extension, a significant change in the suction pressure peak in the chordwise direction is much reduced at a given angle of attack. The leading edge extension can also stabilize the wing vortex on the windward side at angles of yaw, which dominates the vortical flows over yawed delta wings.